In an LTE Release 8 (R8) system, a base station and a terminal communicate and transmit data on a carrier. The terminal scheduled by the base station can have its own physical downlink control channel (Physical Downlink Control Channel, PDCCH for short) in each subframe. Information carried in the PDCCH can be a downlink_grant (Downlink_grant, DL_grant for short) or downlink_Assignment (Downlink_Assignment, DL_Assignment for short), and the DL_grant or DL_Assignment carries scheduling information indicating time frequency resource assignment and the like of a physical downlink shared channel (Physical Downlink Shared Channel, PDSCH for short). The information borne in the PDCCH can also be an uplink_grant (Uownlink_grant, UL_grant for short) or uplink_assignment (Uplink_Assignment, UL_Assignment for short), and the UL_grant or UL_Assignment carries scheduling information indicating time frequency resource assignment and the like of a physical uplink shared channel (Physical Uplink Shared Channel, PUSCH for short). The terminal receives and decodes a PDCCH in a corresponding PDCCH search space, and correspondingly receives downlink data PDSCH or sends uplink data PUSCH. Afterward, the terminal feeds back an uplink ACK/NACK for the downlink data, or the base station feeds back a downlink ACK/NACK for the uplink data, and the downlink ACK/NACK is also called a physical HARQ indicator channel (Physical HARQ Indicator Channel, PHICH for short).
In a time division duplexing (Time Division Duplexing, TDD for short) system, both transmission and reception are completed at different time of a same frequency band, namely, the uplink and the downlink are distinguished based on time. An LTE system can support seven different uplink and downlink subframe configurations, and which uplink and downlink subframe configuration is specifically adopted can be notified to the terminal through a broadcast message.
However, when a PDCCH corresponding to one carrier is sent on the other carrier, if uplink and downlink configurations of the two carriers are not the same, the type of a subframe on the one carrier and that of a subframe, at the same time as that of the one carrier, on the other carrier may be different, and downlink scheduling information or uplink scheduling information on the one carrier cannot be sent on a subframe corresponding to the other carrier, so uplink and downlink scheduling cannot be performed, through the other carrier bearing a PDCCH, on the one carrier bearing no PDCCH.